This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Application No. 2000-33133 filed on Feb. 10, 2000, the entire content of which is incorporated herein by reference.
The present invention generally relates to a lock nut. More particularly, the present invention pertains to a lock nut of the type having a threaded main bore for receiving a threaded portion and a number of oblique bores in each of which is inserted a locking pin for engagement with its forward end against the threaded portion.
A known lock nut is described in UK Patent No. 1,561,946. The purpose of the disclosed lock nut construction is to provide a lock nut with substantially the same locking effect even after repeated use. The lock nut includes a threaded main bore and brass locking pins each shaped as a cylindrical dowel having a smooth outer surface. The locking faces of the pins and the thread of the main bore are machined in the same machining operation. That is, the pins am inserted in their respective oblique bores with the forward end of each locking pin projecting into the not yet threaded main bore of the lock nut. This lock nut is then clamped in a clamping device and is subjected to thread cutting, whereby also the forward ends of the locking pins are cut to form at least one flank each.
When the lock nut is to be arrested to the threaded portion, each locking pin is tightened against the threaded portion by way of a grub screw or the like. The locking faces of the pins are thus pressed against the thread flanks of the threaded portion to give a locking effect provided entirely by friction forces, thereby avoiding deformation of the locking pin. This type of lock nut has proven to provide a reliable and efficient locking effect.
To ascertain that the locking pins are safely retained in their respective oblique bores during the thread cutting operation and afterwards when the lock nut is screwed up on the threaded portion, and without risking that the brass pins move axially in the bores or angularly about their longitudinal axis, it is necessary that each pin fit very snugly into its bore. This means that the fitting of the pins in their respective oblique bores in the lock nut is difficult, and the material forming the pins seizes against the inner surface of the oblique bore.
In light of the foregoing, a need exists for a locking nut that is not as susceptible to the problems and difficulties discussed above.
According to one aspect of the invention, a locking nut possesses a threaded main bore for receiving a threaded portion, with the threaded main bore having an axis and with the thread of the threaded main bore being defined by flanks. The lock nut also includes a plurality of oblique bores in each of which is positioned a respective locking pin having a forward end adapted to engage against the threaded portion, with the forward end of the locking pin being provided with at least one flank. Each oblique bore and the respective locking pin have a common longitudinal axis extending at substantially the same angle to the axis of the threaded main bore as one of the flanks of the thread of the threaded main bore so that the least one flank of the locking pin at the forward end of the locking pin is substantially parallel to said longitudinal axis and lies substantially parallel to portions of said one flank of said threaded main bore adjacent an inner end of the oblique bore. The locking pin is in the from of a substantially cylindrical body having along its outer surface a plurality of evenly spaced apart axially extending serrations that facilitate introduction of the locking pin into its respective bore.
Another aspect of the invention involves the combination of a shaft, a machine member and a locking nut that locks the machine member to the shaft. The locking nut has a main bore provided with an internal thread defined by flanks, and at least a portion of the shaft is positioned in the main bore so that an external thread on the shaft engages the internal thread in the main bore. The lock nut including at least one through bore that is obliquely oriented relative to the main bore and that opens into the main bore. The through bore has an unthreaded first bore portion and a threaded second bore portion, with the first bore portion being located between the main bore and the second bore portion. A locking pin is positioned in the first portion of the through bore and has a forward end that engages the externally threaded portion of the shaft. The forward end of the locking pin has a thread defined by flanks, and at least one flank of the thread of the locking pin at the forward end of the locking pin is substantially parallel to one flank of the threaded main bore adjacent an inner end of the oblique bore. The locking pin is substantially cylindrical and has a plurality of circumferentially spaced apart and axially extending grooves provided in its outer surface. A screw is positioned in the through bore and threadably engages the second portion of the through bore for urging the locking pin towards the shaft.
Another aspect of the invention involves a locking nut which locks a machine member to a shaft, wherein the shaft has an externally threaded portion. The locking nut has a main bore in which is positioned the externally threaded portion of the shaft. The main bore including a thread defined by flanks, and the lock nut includes at least one oblique bore in which is positioned a locking pin having a forward end that engages against the externally threaded portion of the shaft. The forward end of the locking pin has a thread defined by flanks. The the oblique bore and the locking pin have a common longitudinal axis extending at substantially the same angle to the axis of the threaded main bore as one of the flanks of the thread of the threaded main bore so that at least one flank of the thread of the locking pin at the forward end of the locking pin is lies substantially parallel to portions of said one flank of said threaded main bore adjacent an inner end of the oblique bore. The locking pin is substantially cylindrical and has a plurality of axially extending grooves provided in its outer surface. The grooves are spaced circumferentially spaced apart around the outer surface of the locking pin.